Trapezius (traps)A broad, flat, triangular muscle; the two sides together make a trapezoid. It runs from the skull and the spine out to the collarbone and shoulder blade, and it lifts, pulls back and pulls down the shoulder blade.
Latissimus dorsi (lats)Pulls the arm back and in toward the body. It starts on the lower spine, the thoracolumbar fascia, the hip bone and the lowest three ribs. Its fibers gather into a tendon on the humerus.
Thoracolumbar fasciaNot a muscle: a large, roughly diamond-shaped sheet of connective tissue. It wraps the deep back muscles, and the latissimus dorsi starts from it. Older books call it the lumbodorsal fascia.
Levator scapulaeIts name says what it does: it lifts the scapula. A small strap from the top four neck vertebrae to the upper corner of the shoulder blade.
Rhomboid minorSits just above the rhomboid major. It runs from the spines of C7 and T1 to the inner edge of the shoulder blade, level with its ridge. Both rhomboids pull the shoulder blade back toward the spine.
Rhomboid majorPulls the shoulder blade back and turns it. It lies under the trapezius. It runs from the spines of T2 to T5 to the inner edge of the shoulder blade, below its ridge.
Serratus posterior inferiorA thin muscle under the latissimus dorsi. It runs from the spines of T11 to L3 up and out to the lowest four ribs, and it pulls those ribs down.
Deep layers 9
Serratus posterior superiorA thin muscle that lies under the rhomboids. It runs from the spines of C7 to T3 down and out to ribs 2 to 5, and it lifts those ribs.
Splenius capitisTurns the head to its own side. Both sides together tip the head back. It starts on the ligament at the back of the neck and the spines of C7 to T3 and ends on the skull behind the ear.
Splenius cervicisTurns the head and tips the head and neck back. It works with the splenius capitis. It starts on the spines of T3 to T6 and ends on the side processes of the top neck vertebrae.
IliocostalisThe outer column of the erector spinae. It rises from the shared tendon at the hip bone and sacrum and attaches to the angles of the ribs, which is where its name comes from.
LongissimusThe middle and largest column of the erector spinae. It lies between the iliocostalis and the spinalis. It attaches to the lower ribs and the side processes of the vertebrae and reaches the skull behind the ear.
SpinalisThe inner and smallest column of the erector spinae. It runs from spine to spine of the vertebrae, right beside the midline.
Semispinalis capitisThe part of the semispinalis that reaches the skull. The semispinalis starts on the side processes of the vertebrae and is the outermost muscle of the deepest group. It tips the head back and turns it toward the other side.
MultifidusIt lies under the semispinalis and is thickest in the lower back. Its short bundles climb from the sacrum and the vertebrae to the spines of vertebrae a few levels higher, and it steadies the spine.
Quadratus lumborum (QL)A thick, four-sided sheet in the back wall of the abdomen. It runs from the crest of the hip bone up to the lowest rib and the lumbar vertebrae, and it bends the spine to the side.
How this list was compiled: Every name and detail line was checked on 2026-09-30 against Gray, Anatomy of the Human Body, 20th edition, 1918 (public domain), the chapters on the muscles of the back, https://archive.org/details/anatomyofhumanbo00grayrich; TeachMeAnatomy, the superficial, intermediate and deep (intrinsic) back muscles, https://teachmeanatomy.info/back/muscles/superficial/, https://teachmeanatomy.info/back/muscles/intermediate/, https://teachmeanatomy.info/back/muscles/intrinsic/, and its posterior abdominal wall page for the quadratus lumborum, https://teachmeanatomy.info/abdomen/muscles/posterior-wall/; and Kenhub, Back muscles, https://www.kenhub.com/en/library/anatomy/overview-of-back-muscles, and Thoracolumbar fascia, https://www.kenhub.com/en/library/anatomy/thoracolumbar-fascia. The wording is in our own words. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work
How it works
A trunk from behind, drawn twice. The first drawing is a superficial back muscles quiz, with two muscles lifted off the right half. The second goes under them to the long columns beside the spine and the muscles below those.
Read the full guide
Outer layers: muscles that move the shoulder
On the left half the trapezius and latissimus dorsi cover almost everything, with the thoracolumbar fascia between them. On the right half they are removed: the levator scapulae and the two rhomboids run to the shoulder blade, and the serratus posterior inferior reaches the last ribs.
Deep layers: muscles that move the spine
This drawing is the deep back muscles quiz. The left half shows the splenius pair and the erector spinae as three columns: iliocostalis outside, longissimus in the middle, spinalis against the spine. The right half goes deeper still, to the semispinalis capitis, the multifidus and the quadratus lumborum.
Erector spinae from the outside in: iliocostalis, longissimus, spinalis. The longissimus is the largest and the spinalis the smallest.
Rhomboid minor sits above rhomboid major, and it is the narrower of the two.
Two serratus posterior muscles: the superior one lifts the upper ribs, the inferior one pulls the lowest ribs down.
Questions and answers
What are the deep muscles of the back?
They are the intrinsic muscles, which move the spine: the splenius pair, the three columns of the erector spinae, and under them the semispinalis, multifidus and rotatores. The second drawing shows the deep muscles of the back labeled as you name them.
What are the three erector spinae muscles?
Iliocostalis, longissimus and spinalis. They share one tendon at the sacrum and hip bone and run up the back as three columns, the iliocostalis farthest from the spine and the spinalis closest to it.
Which muscles are on an intrinsic back muscles quiz?
Only the deep ones. The trapezius, latissimus dorsi, levator scapulae and rhomboids are extrinsic: they lie on the back but move the shoulder and arm. So do the two serratus posterior muscles, which attach to the ribs.
Is the thoracolumbar fascia a muscle?
No. It is a roughly diamond-shaped sheet of connective tissue over the lower back. It wraps the deep back muscles, and the latissimus dorsi starts from it.